The present invention relates to an audio reproducing apparatus for reproducing a quality signal in a rather noisy environment.
FIG. 8 is a block diagram illustrating a conventional audio reproducing apparatus. In FIG. 8, an input signal received by input terminal 1 is fed into power amplifier 3 via gain-control-circuit 2. An output signal supplied from power amplifier 3 is fed into speaker 4 mounted to baffle 5 and then reproduced. Microphone 6 disposed around speaker 4 collects signals radiated from speaker 4 together with the noises around baffle 5. An output signal supplied from microphone 6 and the output signal from amplifier 3 are fed into subtractor 7, where the input signal component is deducted from the sum of the radiated signal from speaker 4 and the noise around, thereby extracting the noise component around baffle 5. An output signal supplied from subtractor 7 is proportionate to the noise around and restricts a bandwidth of the noise around via low-pass-filter 8. An output supplied from low-pass-filter 8 is converted from ac to dc by rectifying circuit 9 and then supplied to gain-control-circuit 2 disposed at a stage before amplifier 3. This structure allows gain-control-circuit 2 to change automatically an amplitude of an input signal responsive to the noise around speaker 4 so that the signal radiated from speaker 4 can be prevented from being masked by the noise around.
However, a conventional audio reproducing apparatus produces a difference between a signal component radiated from speaker 4 and that supplied from amplifier 3, thus subtractor 7 cannot completely remove the signal component radiated from speaker 4. Therefore, the noise component around the speaker is hard to be extracted, whereby the noises within only a limited bandwidth can be restricted.
The present invention aims to provide an audio reproducing apparatus that removes a signal radiated from a speaker correctly, and changes a gain responsive to noises around.
In order to achieve this objective, the audio reproducing apparatus of the present invention prepares a microphone disposed around a speaker and a detecting means for detecting a movement of a voice coil of the speaker. The microphone and the detecting means extract a noise component around. This structure allows the noise component around the speaker to be extracted correctly, so that masking compensation can be performed in a natural manner.